Geosynchronous Satellite Launch Vehicle (GSLV) is capable of placing 2 ton class of satellites like the INSAT and GSAT series of communication satellites into Geosynchronous Transfer Orbit (GTO). GSLV is a 49 m tall, three stage vehicle with a lift-off mass of 416 ton. The first stage comprises of a S139 solid booster with four liquid strap-on motors, each weighing 40 ton. The second stage (GS2) is a liquid engine carrying 37.5 ton of liquid propellant. The third stage is the indigenously built Cryogenic Upper Stage (CUS) which uses typically 15 ton of cryogenic propellants (Liquid Hydrogen (LH2) as fuel and Liquid Oxygen (LOX) as Oxidiser).

Cryogenic Upper Stage

The Cryogenic Upper stage employs the vital technology that enhances the payload capability to make the vehicle suitable for launching communication satellites. India is the sixth among the space faring countries to develop and test this technology, which is challenging considering the special materials, alloys and fabrication processes required. Equally challenging was the facilities established for testing the ignition and operation of the engine, particularly under vacuum conditions. The year 2014 witnessed the marvellous success of the fifth developmental flight of GSLV with indigenously developed cryogenic stage (CUS-05) from Sriharikota on January 5 successfully placing the GSAT-14 satellite, weighing 1982 kg, in a precise Geo synchronous Transfer Orbit.